Abstract : This study analyzes the impact of risk taking and risk avoidance by the opposing operational commanders in the Peninsula Campaign of the American Civil War. General McClellan's superior force lost this campaign primarily as a result of his risk-avoidance, while General Lee accepted risk and won. The purpose of this study is to determine what factors influenced risk taking by these two generals, and how that knowledge can aid contemporary operational commanders and their leaders. The analysis begins with a review of the meaning and relevance of operational risk, followed by a summary of the Peninsula Campaign. The inquiry into risk taking begins with an examination of the leaders themselves and their personal qualities which affected their ability to accept risk. The investigation continues by probing the impact of political involvement and battlefield conditions on McClellan and Lee's risk taking. The study concludes that McClellan lost the campaign because he failed to accept risk while his adversary exploited such opportunities. McClellan's inadequate moral courage, his perception of political meddling, and inadequate intelligence system, combined to limit his ability to accept risk. (sdw)